Efficacy and safety of guanfacine extended-release in Japanese adults with attention-deficit/hyperactivity disorder: Exploratory post hoc subgroup analyses of a randomized, double-blind, placebo-controlled study

Guanfacine for the Treatment of Attention-Deficit Hyperactivity Disorder: An Updated Systematic Review and Meta-Analysis

Background: Non-stimulant guanfacine is a common second-line medication for attention-deficit hyperactivity disorder (ADHD). Numerous randomized controlled trials (RCTs) have explored the efficacy of guanfacine in ADHD treatment. This meta-analysis combined data from selected RCTs to analyze the efficacy and safety of guanfacine in treating ADHD. Methods: RCTs were identified from published sources through searches in PubMed, Cochrane Library, Web of Science, and Embase (up to February 2022), defining the Clinical Global Impression of Improvement (CGI-I) treatment response score of ≤2 as the primary outcome. Subgroup analysis was performed with a bound treatment duration of 10 weeks. Safety was defined by treatment-emergent adverse events (TEAEs). Results: Twelve out of 332 studies with 2653 participants were included. All studies compared guanfacine with placebos. Guanfacine was significantly more effective in treating ADHD (Risk Ratio [RR] 1.78, 95% CI: 1.59-2.01). In the <10 weeks subgroup, the efficacy in the guanfacine group compared with the placebo group was 58.5% versus 29.4%, respectively (RR 1.97, 95% CI: 1.71-2.26). In the >10 weeks subgroup, the efficacy in the guanfacine group compared with the placebo group was 63.6% versus 39.7%, respectively (RR 1.57, 95% CI: 1.37-1.79). Both subgroups lacked heterogeneity (I² = 0), and a funnel plot showed a low publication bias risk. Around 80% of participants in the guanfacine group experienced at least one TEAE, compared with 66.5% in the placebo group (RR 1.23, 95% CI: 1.14-1.32), with low heterogeneity (I² = 46, p = 0.05). The most common TEAEs in the guanfacine group were somnolence (38.6%), headaches (20.5%), and fatigue (15.2%). Conclusions: Guanfacine is safe and effective for treating ADHD, with no serious adverse events. Guanfacine should be considered as an effective treatment option where effectiveness or tolerability of the central nervous system stimulant is of concern. There is stronger evidence of efficacy for children; more clinical studies are needed for adults.

Efficacy and safety of guanfacine extended-release in Japanese adults with attention-deficit/hyperactivity disorder: Exploratory post hoc subgroup analyses of a randomized, double-blind, placebo-controlled study

Aim

Previously, we reported on the efficacy and safety of guanfacine extended‐release (GXR) in Japanese adults with attention‐deficit/hyperactivity disorder (ADHD) from a phase 3, double‐blind, placebo‐controlled, randomized trial. In this exploratory post hoc analysis, we assessed the efficacy and/or safety of GXR in the following subgroups: ADHD‐combined (ADHD‐C) and ADHD‐predominantly inattentive (ADHD‐I) subtypes, age (≥31, <31 years), sex (male, female), and body weight (≥50, <50 kg).

Methods

The primary efficacy endpoint was change from baseline in the Japanese version of the investigator‐rated ADHD‐Rating Scale‐IV (ADHD‐RS‐IV) with adult prompts (total scores) at week 10.

Results

The efficacy analysis population included 200 patients (GXR, 100; placebo, 100). ADHD‐RS‐IV total score effect sizes (GXR vs placebo) were similar across all subgroups (total population: 0.52, ADHD‐C: 0.51, ADHD‐I: 0.52, ≥31 years: 0.61, <31 years: 0.47, male: 0.50, female: 0.57). There were no major differences in the incidence/types of treatment‐emergent adverse events (TEAEs) across the subgroups. The incidence of significant TEAEs (34.3%, 10.6%) and TEAEs leading to discontinuation (34.3%, 12.1%) were approximately three times higher in females than males, respectively. The incidence of TEAEs in patients weighing <50 kg and ≥50 kg was 100% and 73.6% during dose optimization and 40% and 24.4% during the maintenance period, respectively.

Conclusion

Findings from this post hoc analysis in adults with ADHD support the efficacy and safety of GXR regardless of ADHD subtype, age, or sex and suggest that careful monitoring for TEAEs and GXR dose optimization is considered for all patients, as needed.

In this exploratory post hoc analysis, we assessed the efficacy and/or safety of guanfacine extended release (GXR) in the following subgroups: attention‐deficit/hyperactivity disorder (ADHD) subtypes (ADHD‐combined, ADHD‐predominantly inattentive), age (≥31 years, <31 years), sex (male, female), and body weight (<50 kg, ≥50 kg). ADHD‐Rating Scale‐IV with adult prompts total score effect sizes (GXR vs placebo at 10 weeks) were similar across all subgroups. The findings support the efficacy and safety of GXR in adults regardless of ADHD subtype, age, or sex and suggest that careful monitoring for TEAEs and GXR dose optimization is considered for all patients, as needed.